AA-issued revenue ticket with one trans-Tasman segment on QF, booked as AA codeshare number.
After making the reservation I was able to pick a seat on the QF website and the seat shows when I look up the itinerary on both the QF and AA websites.
When I now try to change the seat on the QF website, I see an "Individual seat selection isn't available for this flight. Select a seat preference" message. Not that I necessarily need to change the seat, but it'd be nice to have the option.
Any workarounds available other than calling QF?

For reference, I have the same itinerary booked for a couple of months later, but on that itinerary (which is an award trip), the trans-Tasman is booked under the QF flight number. For that itinerary I am able to change seats.